1. Field of the Invention
This invention pertains to a clamp having a built-in load limitation mechanism and comprising a clamp body and an actuating device, constructed and arranged so that manipulation of the actuating device results in a corresponding contraction or expansion of the clamp body, thereby exerting a uniform and controlled force on a tubular structure held thereby.
2. Description of the Related Art
Known clamp devices suitable for holding tubes or hoses are described below and are depicted in FIGS. 1 and 2. FIG. 1 shows a prior art clamp 10 comprising a curved resilient portion 12. Extending from the curved resilient portion 12 is a first post 14 with an unthreaded hole 22 located at the free end of first post 14. Also extending from an opposite end of the curved resilient portion 12 is a second post 16, and extending from the end of the second post 16 is a projection 18. The projection 18 has a threaded hole 24 coaxially aligned with and directly opposed to the unthreaded hole 22 found at the free end of first post 14. The clamp 10 also has a screw 20 having a head 26 and threaded shaft 28. The shaft 28 of screw 20 is inserted through the unthreaded hole 22 and then screwed into the threaded hole 24. As the screw 20 is tightened into hole 24, head 26 engages post 14 forcing the two posts 14 and 16 together, thereby causing the curved resilient portion 12 to deflect in such a manner that its radius will decrease. Deflection of the curved resilient portion 12 will cause it to clamp down on any tubular structure that it may hold. Likewise, when the screw 20 is loosened the curved resilient portion 12, assuming that the aforementioned deflection is elastic, will expand as the two posts 14 and 16 move away from each other.
FIG. 2 shows a circular clamp 30 comprising a circular arc portion 32 having a first end 34 and a second end 36. An unthreaded hole 40 is provided in the first end 34 of the circular clamp 30, and a threaded hole 42, which is coaxially aligned with hole 40, is provided in the second end 36 of the circular clamp 30. Furthermore, the circular clamp 30 also has a screw 38 having a threaded shaft 46 and a head 44. The shaft 46 of screw 38 is first inserted through the unthreaded hole 40 and then screwed into the threaded hole 42. As the screw 38 is tightened, the head 44 engages the first end 34, thereby forcing the first and second ends 34 and 36 of the circular clamp 30 together. This causes the circular arc portion 32 of the circular clamp 30 to contract radially and clamp down on any tubular structure that it may hold. Likewise, when the screw 38 is loosened, the circular arc portion 32 will expand as the two ends 34 and 36 move away from each other.
While the two clamps illustrated in FIGS. 1 and 2 may be able to hold certain tubular structures, these clamps lack a mechanism for limiting the amount of force they exert on such structures. Such a force-limiting mechanism is an important feature that acts to prevent unlimited generation of clamping forces, which can cause breakage, cracking, and/or buckling of brittle or pliable tubular structures. The prior art clamps tighten down as the screw is tightened without any means for limiting the amount of contraction and force exerted by the clamp as a result of the screw being tightened. While these clamps may be suited for strong tubular structures made from materials which can sustain relatively large clamping forces without buckling or breaking, such as steel or thick plastic, they are not suited for tubular structures, such as those made of brittle materials such as glass, or pliable materials such as aluminum, which are delicate and can be easily cracked, broken or buckled if subjected to large clamping forces.
For example, syringe pumps, which are commonly used in laboratory and medical instrumentation applications, include syringe mechanisms having tubular barrels made from ground glass, a very delicate material vulnerable to cracking when subjected to point contact forces. Clamps are placed on syringes as anti-rotation devices to prevent the syringes from unthreading and losing vacuum during cycling of the pumps and vibration of the instrument. Clamps without a force limiting mechanism, however, can cause delicate syringe barrels to crack or deform, resulting in broken barrels, leaks, and wasted material.
For the foregoing reasons, there is a need for a clamp apparatus which evenly distributes the force it exerts on tubular structures and also has a built-in load limitation mechanism, which enables it to hold delicate tubular structures in a snug fashion without causing breakage or cracking of the structure.